This invention relates to plasma torches generally, and more specifically to a platelet cooled electrode for a plasma torch.
Plasma torches are commonly used for cutting, welding and spray bonding of workpieces in numerous applications such as toxic waste disposal, metal processing and ash vitrification. Plasma torches generally operate by directing a plasma consisting of ionized gas particles toward the workpiece. A gas to be ionized is channeled between a pair of electrodes and directed through an orifice at the front end of the torch. A high voltage is applied to the electrodes causing an arc to jump the gap between the electrodes, thereby heating the gas and causing it to ionize. The ionized gas flows through the orifice and appears as an arc or flame. In an alternate application, only a single electrode is used and a transferred or cutting arc jumps from the electrode directly to the workpiece.
During the operation of a conventional plasma torch, the torch becomes very hot, especially the surfaces of the electrodes that are directly exposed to the plasma arc. Sufficient cooling must be provided during normal operation to prevent these electrode surfaces from either melting or deteriorating too rapidly. To cool the electrodes, fluid coolant, such as water or gas, is directed through channels or passageways in the electrodes to transfer heat away from the hot electrode surfaces through convection. Typically, the electrodes are manufactured in one piece and the coolant channels are then machined into the finished electrodes using conventional techniques.
Among the drawbacks with conventional plasma torches is that the process of machining coolant channels into the electrodes is limited. It is extremely difficult to precisely machine the coolant channels so that an effective heat transfer area exists between the channels and the electrode surfaces that are exposed to the hot plasma gas. Therefore, these surfaces overheat and rapidly deteriorate with use.
Another drawback with conventional plasma torches is that the plasma arc passing through the electrodes attaches to the exposed surfaces and rapidly erodes these surfaces. Often, the plasma arc will attach only to specific localized areas on these surfaces which quickly overheats and erodes these areas and substantially decreases the life of the electrode.